Category Archives: B-23 Aircraft

0.24 inches was recorded after 7 AM yesterday, bringing our voluptuous rain total to 0.95 inches1. How nice.

Dry spell ahead now, maybe a LONG one. “Fiddle-dee-dee.”

Yesterday: another day shallow precipitating clouds and “ice multiplication”

Seemed to be another day of “ice multiplication” here in southeast Arizona, a term that was coined in 1969 by Peter Hobbs of the University of Washington when he and his group reported that clouds were snowing on the peaks of the Olympic Mountains when the cloud top temperatures were warmer than -10° C (14° F). They had a hut on the top of Mt. Olympus at 7,000 feet! Lots of stories about that experiment, many swirling around Abdul Alkezweeny, a Peter Hobbs grad student in those days. An aircraft with skis landed up there to bring supplies! Imagine. (Yours truly was not embedded in the Hobbs group at that time.) It was an exciting time in that group, prior to the acquisition of their first research aircraft, WWII B-23 “tail dragger.” Peter himself, did not fly in this with RARE exception. Many flights were quite sickening, bumping around in Cumulus and small Cumulonimbus clouds, spinning around power plants stacks, wings vertical to ground….

In a nostalgic mood, posting this photo of our venerable B-23 research aircraft in which I spent SO MANY hours!

His group’s observations, however, were not the first, but were among many airborne and ground reports in the mid and 1960s that left jaws dropping about how much ice was in clouds at these moderately supercooled temperatures, even in clouds with tops as warm as -4° C. It was believed, in various ways that ice nuclei measurements were made on the ground, or in aircraft measurements, that not much ice would be found in clouds until the top temperatures was lower than -20° C. In fact, it was generally believed that only about one ice particle per liter would be found in clouds with tops as cold at -20° C, while actual observations were telling a much different story.

This discrepancy between measured ice nuclei concentrations is a scientific enigma that is still being investigated today! And it appears that me and you cloud maven juniors out there got to see it again yesterday, the second day in a row to see an cloud-ice enigma (“nigma” for short)!

Let us continue this module by examining the assertion of “ice multiplication” with the TUS balloon soundings for yesterday morning and evening as rendered by IPS MeteoStar:

These soundings strongly suggest at the start and end of the day, that coldest cloud tops were warmer or no colder than -10° C.

However, the fly in the oatmeal here is that a cold front and associated wind shift came through in the mid-morning hours, heralded by an little arcus cloud, and cloud tops would have been somewhat colder during that period of rain; we don’t know for sure how much, and satellite imagery suggested lower temperatures, though possibly due to over-riding CIrrus cloud above the “Nimbostratus” layer that produced the steady light rain.

However, the rain before the front went by, and the very light rain showers that fell in the late afternoon were likely well represented by the TUS soundings. That’s my case! Wish I’d had a cloud-instrumented yesterday and the day before. Woulda got a paper out of it: “Ice multiplication rampant in Arizona!”

Yesterday’s actual clouds

No more hand-waving…. Let’s see if it really was raining near the time of the TUS soundings above. Picture of the day:

5:18 PM. Rainbow goes INTO a RAIN GAUGE! Amazing. Proves that it was raining, though very lightly (RW–) at 5:18 PM, when the sounding profile was likely valid for these light showers. Q. E. D.! Yours for $2,000, today only. Should get a lot of money out of this photo. I had to practically have the camera on the ground to get the right alignment and illusion.8:08 AM. Misty, light rain showers shower on the Catalinas and in Catalina itself.

8:50 AM. Misty light rain continues from relatively shallow clouds. No shafting observed, something that would suggest much taller cloud tops. These were likely “mounding” up there, like rolling hills, mounding the most prior to releasing slightly heavier rain. Here’s where you would be thinking, “Could this be ANOTHER ice multiplication day? Wow, if so.” And, of course, the thought of it being a warm rain process day (no ice, thank you) can’t be ruled out either, since rain can form at below freezing temperatures in clouds, though supercooled raindrops are the most vulnerable to freezing at high temperatures, to go a little deep here, and complex the interpretation some.

That was phase one of yesterday’s weather, rain from shallow clouds.

Phase 2 is, “The front marches in across the OV! Cloud depth not so certain, but is probably not real deep, as inferred from the disappointing amount of rain that fell so lightly from the frontal band in spite of its dramatic entrance, fronted by an arcus, wind shift cloud.”

9:55 AM. Here comes the front and arcus wind shift cloud!10:06 AM. Here the approaching front and wind shift appeared to have jacked up a cloud top near Pusch Ridge. Was thinking, as you were, maybe we’ll get some thunder today.10:14 AM. Arcus cloud rolls fast across the OV; rain follows.10:19 AM. Arcus cloud passes over Sutherland Heights, and light curtains of rain begin to fall from it.11:26 AM. The end is near. The sun became visible after only an hour of steady, very light rain, and a tenth of an inch of rain. Thought there might be a gush in this, but, no. This also points to shallow, mounding or even flat cloud tops, not tall ones. This was not a good sight.

But, as those who live here know, some of our best scenes are AFTER after the rain has stopped and the skies partially clear. Yesterday was no exception. But first, the Stratus, which you don’t see too often:

1:09 PM. Looking north at a Saddebrooke highlight. Stratus is beginning to break up out there.1:11 PM. Stratus in the cold air following the frontal passage (“FROPA”, in weather speak or texting). Not budging yet.1:35 PM. Yep, only 25 or so min later, this! So pretty. Stratus fractus lining the area around Charouleau Gap.2:30 PM.2:57 PM. Cumulus puffing up by the minute. Will they form ice?3:04 PM. Just a pretty scene of Cumulus over there toward Saddlebrooke.4:02 PM. A bit of a surprise as a group of precipitating Stratocumulus like clouds came rushing in. No shafts, suggesting tall tops were seen, so likely again just mounding tops up there.5:24 PM. As the last sprinkles ended and the sun peaked through an opening to the SW, our mountains and clouds lit up with an orange tint. As the air cooled the Stratus fractus clouds (highlighted) again were once again straddling the side of mountains near Charouleau Gap.

Looks like only streamers of high and middle cloud from the tropics as California gets blasted with extremely heavy rains over the next two weeks. Totals in favored central and northern California coastal ranges, and in the central and northern Sierras will fall between 20 and 30 inches of rain during this period. A great place for you and me to be would be near the King Range, Shelter Cove (see below), or Honeydew to see those pounders.

Part of Shelter Cove, CA, with King Range in the background. A coastal jet rams the King Range and causes prodigious rains from ordinary looking storms. Average precip more than 100 inches, farthest south point for such a high average rainfall on the West Coast.

The End

—————————–1The online gauge is a Davis tipping bucket. It has been consistently under-measuring totals recorded in the NWS 8-inch diameter gauge, and the 4-inch diameter, ground-mounted (it sits on the ground among grasses and weeds) CoCoRahs gauge. CoCoRahs is a national organization of rain and snow measuring nuts (haha, just kidding-they’re really precipophiles like me) all over the country and overseas as well. You can find them here. Part of the reason for the under-measurement of the Davis instrument is loss due to wind. That tipping bucket sits up at about 6 feet off the ground, thus sees a lot more wind than gauges on the ground. A gauge on the ground, away from tall objects, is always the best way to go! The reason for this explanation is because if you go to Wundermaps or Weather Underground and see the total for this site, it is ALWAYS going to be low compared to the actual amount that fell. This is a degradation that has come up over the past year or two.